This invention relates to a resin usable as a material for producing plastic (or polymer) lenses, particularly plastic lenses for spectacles, a process for producing such a resin and a plastic lens obtained by using such a resin.
As materials for optical lenses, there have been used acrylic resins, diethylene glycol bisallyl carbonate resins (e.g. CR-39), polystyrenes, polycarbonates, etc., having high transparency. Among these resins, diethylene glycol bisallyl carbonates, which are a thermosetting resin, are widely used as resins for lenses of spectacles, due to having excellent transparency, low dispersion (high Abbe's number), excellent heat resistance and excellent impact strength. But there is a problem in that when the lenses are produced by using the diethylene glycol bisallyl carbonate, the refractive index is as low as 1.50 and the lens thickness becomes larger compared with the case of lens made of glass (this is remarkable in thick-lensed spectacles).
With a recent demand for thin and light-weight spectacle lenses, materials for spectacle lenses having a high refractive index have been developed variously. For example, Japanese Patent Unexamined Publication (JP-A) No. 56-166214 discloses a copolymer of a dimethacrylate having a nuclear halogen-substituted aromatic ring and a monofunctional monomer having an aromatic ring. This material has a high refractive index, but has a problem in that it has a large specific gravity due to having halogen groups in the resin skeleton. Further, JP-A 63-46213 discloses a copolymer of polyisocyanate and polythiol. This material has a high refractive index, but has a problem in that it is low in heat resistance.
On the other hand, as thermoplastic resins having a high refractive index, there are known polystyrenes (refractive index 1.58, Abbe's number 31) and polycarbonates (refractive index 1.58, Abbe's number 30). These resins have a high refractive index, but have a large chromatic aberration due to low Abbe's number. Further the polystyrenes are undesirably low in heat resistance and the polycarbonates are undesirably low in surface hardness and easily scratched. In order to improve such disadvantages, there are proposed methyl methacrylate/styrene resins, and tricyclo[5.2.1.0.sup.2,6 ]deca-8-yl methacrylate/styrene resins (JP-A 62-246001). But these resins have problems in that these resins are high in the haze rate, low in transparency, further the methyl methacrylate/styrene resin is low in heat resistance. In addition, since these resins are thermoplastic resins, there is a problem in edging ability.
Further, JP-A 62-232414 discloses a copolymer of tricyclo[5.2.1.0.sup.2,6 ]deca-8-yl methacrylate/styrene/crosslinkable polyfunctional monomer. This copolymer is insufficient in the haze rate.
But these materials mentioned above are poor in resistance to scratching as in general plastics. In order to improve this, it is proposed to coat the lens surface with an organic silane cured film. Buch such an organic silane cured film is undesirably insufficient in uniform adhesiveness to the plastic lens surface.
In order to improve the surface properties of plastic substrate and to improve adhesiveness to silicone cured film, there are proposed thermoplastic acrylic primer (JP-A 52-138565), acrylic primer having a functional group such as an amino group (JP-A 53-138476), a silicone primary containing a reaction product of alkoxysilane having a functional group such as an amino group or a hydroxyl group and a cyclic acid anhydride (JP-A 53-81533), a silicone primer containing a mixture of a hydrolyzate of epoxysilane and an aminosilane (JP-A 54-63176), an acrylic primer containing a functional group-containing thermoplastic acrylic resin and a ultraviolet absorbing agent (JP-A 55-500809), an acrylic primer containing a thermosetting acrylic emulsion and a ultraviolet screening compound (JP-A 58-160033), a silicone primer containing a reaction product of an aminosilane, an epoxysilane and an acid anhydride (JP-A 56-16573), a process for improving an adhesive strength by coating a melamine modified acrylic emulsion (JP-A 56-88469), a thermoplastic acrylic primer containing a reaction product of an acrylic monomer, an epoxy methacrylate and a hydroxybenzophenone ultraviolet absorbing agent (JP-A 57-23661), a primer containing a self-crosslinkable acrylic copolymer (JP-A 57-76035), a primer containing a polyfunctional vinyl polymer (JP-A 57-140162), a primer containing an acrylic polymer and an alkyltrialkoxysilane (JP-A 57-162729), a primer containing a copolymer of methyl methacrylate and methyl acrylate (JP-A 58-179237), etc.
These materials have been developed depending on individual objects, but are still insufficient for giving sufficient effects for plastic lens substrates.
As mentioned above, there were no resins for plastic lenses having a small specific gravity and satisfying properties required for plastic lenses. Further, there were no plastic lens substrates having a low specific gravity, and there were no primers and no silicone cured films having a sufficient adhesive strength to such plastic lens substrates.